Communicating system



Dec. 26, 1950 w. s. HALSTEAD 2,535,063

COMMUNICATING SYSTEM Filed May '5, 1945 3 Sheets-Sheet 2 INSERT EARPIECEOR OTHER TRANSDUCER WORN 1 ON HEAD OUTPUT AMPLIFIER INPUT TNORMALRECEIVE M 45 so v 49 7- I I q 39 PRESS-TO-TALK T 42 4s CORRECTION INPUTI FILTER 1OUTPUT TO INTERCOMMUNICATION CIRCUIT 4| 4&

FIG. 3

WILLIAM S. HALSTEAD INVENTOR TORNEY HALSTEAD Dec.- 26, 1950COMMUNICATING SYSTEM Fild May 3 19 3 Sheets-Sheet 3 FIG. 4A

TRANSMIT WILLIAM S. HALSTEAD INVENTOR RECEIVE ATTORNEY Patented Dec. 26,1950 umro STATES ATENT orrice ooMMuNIcATING SYSTEM William S. Halstead,Purchase, N. Y., assignor, by mesne assignments, to Farnsworth ResearchCorporation a corporation of Indiana Application May '3, 1945, SerialNo. 591,742

2 Claims. 1

This invention relates to systems for two-way electrical communicationwhere a single trans-- ducer functions both as transmitter and asreceiver.

In two-way electrical communication systems, it has hitherto been theusual practice to employ two separate transducers, one transducer beingusually placed at, or within auditory range. of the ear of the operator,this transducer serving to convert the received electrical signals intoacoustical energy, which latter will then act upon the physiologicalhearing organs of the operator. The other transducer was usually placedin proximity to the operators mouth, and was elit rayed to pick upspeech as it issued 'dire'ctlyfroin the mouth, and to convert theacoustical energy into e1ee trieai signa s.

In some instances it has been proposed to em ploy a single transducercapable of functioning alternatively in both senses, i. e. to convertelcc trical energy into reproduced sound and to conv'ert sound energyinto electrical wave forms; The use of a single transducer has suffered,inter alia; from the disadvantage that such instrument. if placedsufficiently close to the mouth to act as a transmitter, could not, inthis position, act with equal efficiency asa receiver. One proposedsolution for this difiiculty was to alter the position of the transducerfrom a position adjacent the mouth to one adjacent the ear, whenever reception was initiated, and to make-Ia reverse movement of thetransducer, whenever transmission was initiated. Such alteration of theposition of the transducer either demanded that the operator employ hishand to effect such movement, or else that he move his head from oneposition to another, in order to approximate the desired portion of hisheadto the transducer. Either one of these species of movement demandedattention on the part of the operator, which often prevented him fromaccomplishing other needful duties and very frequently the movements ofthe operator were not strictly or properly coordinated, when changingfrom a transmitting to a receiving position, or the received signalswere often lost in part, because, at the moment of reception, thetransducer would be located either near the mouth of the operator, orwould be in transit to or from his ear.

The present invention overcomes the above recited difiiculties and. yetallows the employ-mentof a single transducer. This is accomplished bypermanently locating such transducer either par tial-ly within orclosely adj acent the ear. In such location, the transducer functionssomewhat as a telephone receiver of the well known hearing aid type.When acting as a transmitter; the transducer, remaining in the sameposition, picks up the auditory vibrations which are present within theear or in the bone structure adjacent the ear, or from both suchsources.

One object of this invention is to provide a two-way, or lei-lateraltransducer which may be carried or worn by an individual user in anunobtrusive manner, and which transducer will act without alteration ofposition when change of the function performed is made, fromtransmission to reception, or Vice versa.

Another object of this invention is to provide a bi-lateral transducerwhich is so constructed and located with respect to the person of theoperator that it functions as an ambient noise reducing microphoneduring periods of transmission, and as a similar sound discriminatoryreceiver during periods of reception.

A further object of this invention is to provide a single transducerwhich may be more or less permanently worn by an operator and which mayfunction alternatively for either transmission or reception, withoutrequiring the employment of the operators hands and without anysubstantial interference with, the freedom of movement of the operator.

Yet. another purpose of this invention is to provide, as a single unit,a complete radio transmitter and receiver, having a single transducer,which unit will be highly portable and may be worn upon the person ofthe operator and which will incorporate therein all essential elements,including an antenna.

Still another object of this invention is to provide a bi-lateraltransducer adapted to lie positioned adjacent the ear of the operatorand to be connected to the transmitting and receiving apparatus properby a composite conductor, which conductor functions both to lead speechfrequency currents to and from the transducer, and at the same timefunctions as a radiative and receptive antenna.

A yet further object of this inventionis to provide a transmitting andreceiving unit for use in an intercommunications system, for esample onan aircraft, in which a single transducer is employed at, or adjacentthe operator's ear, and in which, due to such location, the transducerwill function satisfactorily in a milieu of relatively high ambientnoise level, even though such level be sufficiently high to causedifficulties when transmission microphones of conventional types areemployed.

Another purpose of this invention is to employ, in two-way electricalcommunication systems, a transducer which is located partly within theear of the operator and which operates as a transmitter partly bypicking up relatively high frequency sounds transmitted to the operatorsear via the Eustachian tube, and partly by picking up relatively lowfrequency speech vibrations transmitted to the transducer via the bonestructure in or adjacent the operators ear.

Another purpose of this invention is to provide a bi-lateral transducerfitted with a rubber cushion or the like so that when it is inserted asfar as possible within the ear, such cushion will effectively seal offand reject extraneous sound waves, arising from sources external to theoperator.

Other purposes and advantages of this invention will be seen from thefollowing specification and from the drawings hereunto afiixed.

In the drawings:

Fig. 1 is a block diagram of a portable two-way radio telephone unitemploying a single trans ducer according to this invention.

Fig. 2 shows one embodiment of a two-way radio telephone, utilizing thecircuit of Fig. 1, as worn upon the person of the operator.

Fig. 3 is a block diagram of another embodiment of this invention,constituting a single twoway station of a wire intercommunicationsystem.

Fig. 4A shows the bi-lateral transducer of this invention located partlywithin the ear and illustrating the operation of the transducer as atransmitter, and

Fig. 4B is similar to Fig. 4A, but shows the transducer functioning as areceiver.

Theblock diagram of Figure 1 illustrates the arrangement of unitsemployed in the radio communicat ons system of the invention, includinga miniature portable receiver H, a portable transmitter l2, and anaudio-frequency input correction filter Hi having high-pass frequencycharacteristics, all of which are preferably combined in the form of atransceiver 32, having a multicontact switch It to shift from the normalor receive position, to the transmit position. A transducer I8 isprovided for use as an ear hone during reception and as a microphoneduring transmission. The transducer may be-either the insert earphonetype as shown or one of the well-known bone conduction type, notillustrated, the insert type being placed inside the ear and in the caseof the bone conduction type, worn behind the ear, as is common practicein connection with hearing aids.

The antenna 29 is combined with the transducer conducting lead wires 2!into a single flexible cable provided with suitable insulating material,2|, having a low dielectric constant and separating the inner transducerconductors 2i from the outer metallic braided antenna con-.

ductor 20, and also an outside layer, 25 of insulating material forminga protective coating around the antenna conductor 2t (Fig. 4A)

In the normal or receive position, movable contact 23 of switch l5connects to contact 2d, which in turn connects the antenna circuit tothe radiofrequency signalinput circuit of receiver Ii. Movable contact26 connects the transducer E8 to contact 2'5, which in turn connects tothe audio-frequency output circuit of receiver 15. The circuit fromtransducer 3 to receiver H is completed by means of a common groundconall) nection. Spring 25 holds the switch it in the normal or receiveposition.

When the switch It is moved to the transmit position, movable contact 23connects the antenna 20 to the contact 28, which in turn connects theantenna 28 to the radio-frequency output of transmitter l2. When in thetransmit position, the movable arm 25 of switch it; connects thetransducer l8 to the lower contact 25, and thence through theaudio-frequency correction filter l4 to the signal input circuit oftransmitter I2.

The single transducer [8 thus normally functions as a receiver earphoneduring stand-by periods, and'as a microphone when transmitting, withoutneed for the operator to move the transducer from ear to mouth, andwithout requiring the use of the operators hand in holding a microphoneto the mouth, as has been common practice in the past. When transduceris, of the insert" type, is employed in the above-described manner, ithas the added advantage of effecting a material reduction in outsidenoises, this result being obtained largely by virtue of the propertiesof the bone structure of the operators head, which structure haspronounced sound absorbing qualities to external noise and causes greatattenuation of any sound wave energy which may reach the diaphragm ofthe transducer from sources external to the wearer of the transducer.

The audio-frequency filter M is inserted in the transmitter inputcircuit in order to attenuate thepreponderant low frequencies of thehuman voice, as such voice or voice vibrations exist within thestructure of the ear or on the surface of the skull. Without the filter,which attenuates the lower voice frequencies and permits the highfrequencies topass unimpeded from the transducer microphone, the qualityof the voice signals as impressed on the signal input circuit of thetransmitter would be such as would cause seriously distorted orunintelligible voice signals at receiving points, with little if any ofthe higher frequencies above several hundred cycles being evident in thereproduced voice signal. By the use of the correction filter, however,the highfrequency attenuation caused by the acoustic properties of thephysical structure of the ear and head may be corrected or compensated,since the filter may be designed greatly to reduce or substantially toeliminate all frequencies below 200 cycles, and to pass without materialattenuation all frequencies above several hundred cycles. As a furtheraid in this directionythe speech input circuit of the transmitter may bedesigned to effect pre-emphasis of the higher audio frequencies in thevoice frequency spectrum, thus causing additional discrimination infavor of the higher audio frequencies, which latter are required inobtaining a high degree of intelligibility of voice reproduction. It isobvious that a special transducer having a diaphragm which is responsiveto the higher audio frequencies and relatively non-responsive to the lowaudio frequencies, which latter exist in the structure of the head, canalso aid in increasing I intelligibility of the voice signals.

It may be seen from the drawing of Figure 2 that the radio-telephoneshown schematically in Figure 1 may be worn by an operator 3 I, thetransducer l8 being in the form of an insert earpiece fitted into theearof the user, and the combined antenna and transducer cord 26, 21 extending downward fromthe earpiece to the combined transmitter-receiver unit32, which latter may be carried in a'pocket of the operator's clothing,as indicated, worn on a belt (not illustrated), or otherwise suitablysuspended. The transmitreceive switch I6 provides means for shifting thetransceiver from the normal or receive, to the transmit position.

In the diagram of Figure 3, the transducer l8, similar to that shown inFig. 1, is used in connection with wire telephone transmission, such asthat employed in an aircraft. This type of embodiment includes a lineamplifier 35, a correction filter l4, similar tothat shown in Figure 1,in combination with a multi-contact switch 49, this switch providingmeans for shifting the equipment from the normal or receive p osition,to the talking or transmitting position. Transducer l8 functionsalternatively as an earphone or a microphone, depending upon itsconnection through switch 49 to the output circuit or input circuit,respectively, of amplifier 35, and is worn on the head of the user, aspreviously described.

In the normal or receive position, movable arm 36 of switch 49 connectsthe transducer 8 to contact 31, which latter in turn connects to contact38 and thence through movable arm 39 to the output circuit of amplifier35. The intercommunication circuit, or line, having terminals 48,connects through line 4| to contact 42 and ground, and thence fromcontact 42 through movable arm 43 to the input circuit of amp ifier 35,thereby completing the receiving circuit from line 4| to the transducerl8. In the embodiment shown in this figure, all circuits have a commonground connection, as indicated by conventional symbo s.

When switch 49 is in the press-to-talk position, transducer l8 functionsas a microphone, in the manner described in connection with Fig. 1. Whenswitch 48 is in the above-mentioned position, transducer I8 is connectedthrough movable arm 36 to lower contact 45, thence through thecorrection filter l4 to lower contact 45, and throu h movable arm 43 tothe input c rcuit of am lifier 35. The output circuit of amplifier 35connects to movable arm 38, of switch 49 and thence to low r contact 41,which latter connects as shown, to the inter-communication line 4| andtermina s 48 which latter can connect with a line extending to one ormore inter-communication units of the type shown in Figure 3, or ofother suitable ty es.

In the same manner as that described in Fig. 1. the transd cer I 8functions as a receiver earphone when receiving, or as a microphone whenV talking, without any need for the operator to hold a microphone to hismouth or to move the transducer l8 from ear to mouth, the correctionhigh-pass filter l4 being used to overcome the obiectional preponderanceof low frequencies present in the bone structure of the head, whentalking. Inasmuch as the transducer I8, when in the form of an insertearphone, is sensitive principally to voice energy transmitted throughthe bone structure of the head and passages of the ear, such as theouter ear passage known as the external auditory means. and isrelatively insensitive to ambient noise originating outside of the head,a marked discrimination in favor of the operators voice is obtained. Thesystem is thus well-adapted for use in aircraft where high ambient noiselevels are present.

Figures 4A and 4B illustrate the cross section of a human ear and itsadjacent area, and also show the application of transducer unit I8 tothe car,

forthe dual purpose of transmitting and receivmg.

In Fig. 4A is shown the transducer |8 in position to function as amicrophone. The soft rubber cushion |8A serves two purposes, first toprovide comfort and ease of wearing for the operator, and secondly, toeffectively seal off and reject substantially all extraneous sound wavesfrom sources external to the wearers ear. The ear insert section IBB,shown in simple form, may be of a size and shape to fit the individualear. This insert piece provides a protective housing for the microphonel8 diaphragm, and also contains an unobstructed passageway or cavity,through which, sound waves or vibrations, or the combination of 'both,may proceed, in order to exert a driving force upon the diaphragm of themicrophone l8.

This actuation of the microphone I8 is dependent upon the sum of variouseffects created in the ear and its surrounding area during the time whenan individual is speaking. There is utilized the combined effect ofsound waves that are present in the internal auditory area, coupled withskull conduction vibrations, or pressures due to acoustic resonances, inorder to take advantage of all media for sound transmission.

The sound travels in the direction of the transducer unit l8, as shownby arrows in Fig. 4A, and the consequent diaphragm displacement withintransducer l8 results in the generation of an electrical output, whichlatter is then fed through the twin conductors 2| to correction highpass filter M, for low frequency attenuation.

Fig. 4B represents the identical transducer l8 unit serving as areceiver earphone. Its operation in this casein no essential waydeviates from that of the typical hearing aid phone, and itsconstructional aspects are, in all respects, similar to hearing aid typereproducers. Audio frequency signal energy is applied to the conductors2| of the earphone cord, which conductors are connected to thereproducing system of transducer l8, and the consequent sound waves areimpressed upon the wearer's auditory nerves via the usual inter-auralacoustical path. The direction of sound travel is indicated by the arrowshown in Fig. 4B.

The previously described methods of sound pickup and reproduction, foruse in conjunction with the portab e two way radiotelephone system, suchas that shown and described in Figs. 1, 2 and 3, may also be practicedwhen using a bone conduction type transducer and suitable correctionhigh pass filter, as previously mentioned.

What-is claimed as new and desired to secure by Letters Patent of theUnited States, is:

1. A combination transmitter-receiver, including a transmitter proper,a. receiver proper, a transducer adapted to be positioned adjacent theentrance of the ear of an operator, a cord alternatively leading lowfrequency energy to and from said transducer, a layer of relatively lowdielectric material surrounding said cord, a layer of conductivematerial embracing said dielectric layer and functioning as antennameans, switching means connecting said transducer alternatively to theinput of the transmitter proper and to the output of the receiverproper, said switching means simultaneously connecting said antennameans alternatively to the output of the transmitter proper and to theinput of the receiver proper, said combination also including speechfrequency corrective means connected between said transducer and theinput of said transmitter proper, whereby the distortion of acousticalenergy reaching said transducer via the ear is compensated.

2. In a communication system of the type described, including anearphone adapted to be situated at the entrance of the ear, acombination telephone cord and antenna, comprising a twin conductorextending to said earphone and conducting speech frequency currentsthereto and therefrom, an antenna formed as a metallic cylindersurrounding and coaxial with the mean centre of said twin conductor, andan insulating material of low dielectric constant substantially fillingthe space between said conductor and said antenna.

WILLIAM S. HALSTEAD.

REFERENCES CITED The following references are of record in the 'file ofthis patent? Number I 15 Number 8 UNITED STATES PATENTS Name DatePridham Oct. 19,1920 Fox 1 Oct. 9, 1934 Johnson June 16, 1936 BallantineJune 28, 1938 Ballantine June 28, 1938 Koch Feb. 28, 1939 Cover June 2,1942 V Perlman May 18, 1943 Hansell June 1, 1943 Olson Feb. 8, 1949FOREIGN PATENTS Country Date Germany Oct. 6, 1919

